Tobacco-smoke filters

ABSTRACT

A tobacco-smoke filter includes a granular compound or substance comprising silver permanganate and zinc oxide and acting as a catalyst for the oxidation in combination with chloramine-T for preventing poisoning of the catalyst by tobacco-smoke. For instance, the catalyst compound or substance may be interposed between a mouth-end filter section of cellulose-acetate and a filter section of paper soaked in a solution of the chloramineT.

United States Patent [151 3,693,632 Tolman 1451 Sept. 26, 1972 [54]TOBACCO-SMOKE FILTERS [56] References Cited [72] Inventor: ThomasWilliam Charles Tolman, UNITED STATES PATENTS Eastleigh, England3,251,365 5/1966 Keith et a]. ..13 1/265 X 1 Ass1snee= Brown andWilliamson Tobacco 3,368,566 2/1968 Avedikian ..131/10.7 Corporation,Louisville, y- 3,434,479 3/l969 Till et al. ..l3l/l0.9

[22] Filed: April 7, 1971 Primary Examiner-Melvm D. Rein PP 132,212Attorney-Kane, Dalsimer, Kane, Sullivan and Kurucz [30] ForeignApplication Priority Data 7 ABSTRACT A tobacco-smoke filter includes agranular compound 1970 Great Bmam "1&757/70 or substance comprisingsilver permanganate and zinc oxide and acting as a catalyst for theoxidation in combination with chloramine-T for preventing poisoning [521U.S. c1 ..131/266, 131/262 A, 252/411 s of the catalyst by tobacwsmoke.For instance, the lilt- Cl. t l t compound or substance may beinterposed Fleld of search-252ml 429 R; 131/261 between a mouth-endfilter section of cellulose- 13 1/264-267 acetate and a filter sectionof paper soaked in a solution of the chloramine-T.

3 Claims, No Drawings TOBACCO-SMOKE FILTERS This invention concernsimprovements relating to tobacco-smoke filters for cigarettes and othersmoking articles.

It is well known that the smoke from burning tobacco contains 'a widevariety of different chemical .substances which may be wholly in eitherthe particulate or the vapor phase of the smoke, or partially in bothphases. Many of these substances contribute nothing pleasant to thetaste or aroma of the smoke. There are some in the vapor phase which itmay be preferred to eliminate or reduce substantially, such for exampleas carbon monoxide.

Among filters which have been proposed are various filters comprising asolid absorbent, such as activated charcoal, alumina or the like,contained between two plugs of other material, generally conventionalfiltering material. impregnation of the absorbent with various materialsin order to improve the adsorption of specific constituents of tobaccosmoke has also been proposed. Filters containing such adsorbents haveusually been of limited effectiveness.

It is an object of the present invention to provide a tobacco-smokefilter which is capable of removing substantial quantities of carbonmonoxide without adversely affecting the taste of the smoke.

According to the invention, a filter for tobaccosmoke includes agranular compound or substance comprising silver permanganate and zincoxide and acting as a catalyst for the oxidation of carbon monoxide tocarbon dioxide, in combination with chloramine-T for preventingpoisoning of the catalyst.

As is known, the activity of a catalyst may be suppressed by thepresence of certain other substances, so that it appears to be poisoned.With cigarette smoke, catalyst poisoning may occur due to the presenceof sulphur-bearing compounds. Such poisoning is effectively prevented bythe chloramine-T.

Advantageously, the catalyst is prepared in the following manner:

Silver nitrate (8 g) is dissolved in distilled water (12 ml). Thissolution is then added slowly, with stirring, to finely powdered zincoxide (7 g) and the mixture is worked to a smooth paste. Potassiumpermanganate (8.3 g) dissolved in distilled water (120 ml) is added tothe zinc oxide/silver nitrate paste while stirring vigorously, stirringbeing continued for about one hour. The resultant slurry is cooled to atemperature of about l 7 C and maintained at that temperature for about2 hours. The cold slurry is filtered through a sintered glass funnel andwashed with five portions (each 5 ml) of cold distilled water. Thefiltrate is removed from the funnel and left to dry, as a cake, underambient conditions. The semi-dry residue is pressed into pellets using apressure of approximately 10 tons per sq. inch. The pellets are crushedand sieved to a mesh-size range of 0.30-0.7l mm (22-52 BritishStandard). The granular silver permanganate/zinc oxide catalyst thusproduced contains 34 mole percent of silver permanganate.

A filter incorporating the catalyst, thus prepared, in combination withchloramine-T may be prepared in the following manner:

mm long, consisting of paper which has been soaked in a 10 percentaqueous solution of chloramine-T, giving a composite filter of 35 mmtotal length.

Such filters were attached to cigarettes and smoked, using a smokingengine which provided one puff per minute of 2 seconds duration and 35ml volume. On analysis of the smoke from the cigarettes, it was foundthat 50-60 percent carbon monoxide had been removed.

The use of an aqueous solution of chloramine-T was preferred, as thepresence of water was found to enhance the activity of the chloramine-Tand hence the efiiciency of the catalyst.

Further specific examples of the use of the granular AgMn0 /ZnO will nowbe described:

EXAMPLE 1 Triple filters, 30 mm long, were prepared in which the centersection, 10 mm long, was composed of 1,000 mg of the granular AgMnOJZnO.The filter section, 5 mm long, at the mouth-end consisted of celluloseacetate and the other section, 15 mm long, was made of paper which hadbeen impregnated with a 10 percent aqueous solution of chloramine-T. Thefilters were attached to cigarettes and smoked using a smoking en'- ginewhich provided one puff per minute of 2 seconds duration and 35 mlvolume. On analysis of the smoke from the cigarettes, it was found that41 percent carbon monoxide had been removed.

EXAMPLE 2 On smoking cigarettes through a similar filter, 40 mm long, ofwhich the center section, 20 mm long, was composed of 2,000 mg of thegranular AgMnO /Zn0, the reduction in carbon monoxide was 68 percent.

For comparison purposes, cigarettes were smoked 7 through a triplefilter, 35 mm long, in which 1,500 mg of the granular AgMnO /ZnO wasinterposed between a mouth-end section, 5 mm long, consisting ofcellulose acetate and a section, 15 mm long, consisting of paper whichhad not been treated with chloramine-T. The reduction in carbon monoxidewas less than 10 percent.

Also for comparison purposes, cigarettes were smoked through a dualfilter of which one section consisted of cellulose acetate and thesecond of paper which had been impregnated with a 10 percent solution ofchloramine-T. The reduction in carbon monoxide was zero.

It will be seen from the examples that AgMnOJZnO is an effectivecatalyst for the oxidation of carbon monoxide to carbon dioxide and thatthe poisoning effect of tobacco smoke in reducing catalytic activity islargely prevented by the use of chloramine-T.

Iclaim:

l. A tobacco-smoke filter conforming to the cross section of a tobaccosmoking article including a granular substance comprising silverpermanganate and zinc oxide and acting as a catalyst for the oxidationof carbon monoxide to carbondioxide, in combination with chloramine-Tfor preventing poisoning of the catalyst.

2. A sectional filter as claimed in claim 1, wherein than thatcomprising the catalyst substance.

3. A sectional filter as claimed in claim 1, wherein the catalystSubstance is interposed between a mouthend filter section ofcellulose-acetate and a filter section of paper soaked in a solution ofthe chloramine-T.

2. A sectional filter as claimed in claim 1, wherein the chloramine-T isprovided in a filter section other than that comprising the catalystsubstance.
 3. A sectional filter as claimed in claim 1, wherein thecatalyst substance is interposed between a mouth-end filter section ofcellulose-acetate and a filter section of paper soaked in a solution ofthe chloramine-T.